Regional Update, Influenza and Other Respiratory Viruses. Epidemiological Week 34 (30 August 2024)

ABSTRACT

[WEEKLY SUMMARY]. Regional Situation During the last four epidemiological weeks (EW), there has been a decrease in the activity of Influenza- Like Illness (ILI). Activity has been observed in the Southern Cone, the Caribbean, and Central America. This activity is linked to the circulation of RSV in the Southern Cone and Central America, influenza in the Caribbean, and SARS-CoV-2 in North America, the Caribbean, and Central America. Additionally, epidemic levels of Severe Acute Respiratory Infection (SARI) have been observed in the Southern Cone, the Andean subregion, and Central America, related to positive cases of RSV, and to a lesser extent, influenza. In North America, there has been an increase in activity related to the circulation of SARS-CoV-2. Regarding the circulation of respiratory viruses at the regional level, SARS-CoV-2 activity has increased, particularly in North America, the Caribbean, and the Andean subregion. Additionally, although influenza activity has decreased, it remains fluctuating in some Caribbean countries and the Andean subregion. RSV activity has reached epidemic levels in Central America, the Andean subregion, and the Southern Cone. North America Cases of ILI, SARI, and hospitalizations associated with respiratory viruses, after showing an increase in recent weeks, have begun to decline, although the majority of positive cases are attributable to SARS-CoV-2. Influenza activity has remained below the epidemic threshold in all countries. During this period, the predominant influenza viruses have been A(H3N2), followed by A(H1N1)pdm09 and B/Victoria. RSV activity has remained low. In contrast, SARS-CoV-2 activity has remained at levels similar to the peaks observed in the previous 2023-2024 wave. By country • In Canada, SARS-CoV-2 activity has increased, reaching levels close to the peaks recorded in previous waves. Influenza activity remains below the epidemic threshold, while RSV activity remains low. • In Mexico, after rising to moderate levels in previous epidemiological weeks, ILI and SARI cases have shown a marked decline in the last four weeks. Most positive cases are attributable to SARS-CoV-2, which is currently declining. Both influenza and RSV activity remain low. • In the United States, the hospitalization rate associated with SARS-CoV-2 per 100,000 inhabitants has shown a decline in the last three weeks, and SARS-CoV-2 positivity rates have reached values similar to the peaks observed in 2023 and 2024. Influenza and RSV activity continue to remain low. Caribbean Following the rise observed in previous weeks, ILI cases have shown a decreasing trend over the past four EW, associated with a higher proportion of positive influenza cases. SARI cases have remained low. Influenza activity has fluctuated, though declining at moderate levels over the past four EW, with A(H3N2) being predominant, followed by A(H1N1)pdm09. RSV activity has remained low, though showing a slight increase, and SARS-CoV-2 activity remains high. By country In the last four EW, influenza activity has been observed in Belize, the Dominican Republic, and Guyana. Additionally, SARSCoV- 2 activity has been recorded in Belize, Jamaica, Barbados, Guyana, the Cayman Islands, and Saint Vincent and the Grenadines. • In Guyana, following an increase in ILI and SARI activity in previous weeks, a decline has been observed in the last two EW, with positive cases attributable to influenza, and to a lesser extent, SARS-CoV-2. Central America After the increase in ILI and SARI activity observed in previous weeks, there has been a decline in the last three EW, with most positive cases attributable to SARS-CoV-2 and RSV, whose activity has shown an upward trend. Influenza activity, after reaching epidemic levels in several countries in the subregion, has declined over the past four EW. During this period, the predominant influenza viruses have been A(H3N2). RSV activity continues to rise, reaching levels similar to the peaks recorded in previous seasons. After reaching levels similar to the peaks observed in previous waves, SARS-CoV-2 activity has shown a downward trend over the past four EW. By country • In Costa Rica, following the increase in ILI and SARI cases in previous weeks, a decreasing trend has been observed over the past four EW, with most positive cases attributable to SARS-CoV-2, whose activity is declining, and to a lesser extent, influenza, which is currently declining below the epidemic threshold. RSV activity has shown a slight increase, although it remains low. • In El Salvador, after reaching moderate levels, influenza circulation has shown a decline over the past four EW, falling below the epidemic threshold. SARS-CoV-2 has shown an increase, although it remains low compared to previous waves. • In Guatemala, there has been an increase in ILI activity to moderate levels, with most positive cases attributable to SARSCoV- 2, and to a lesser extent, influenza and RSV. SARI activity has increased to epidemic levels, with a significant rise in the proportion of positive RSV cases. • In Honduras, over the past four EW, SARI activity has fluctuated at epidemic levels, mainly associated with positive influenza cases, which are currently at epidemic levels, and to a lesser extent, SARS-CoV-2 and RSV. • In Nicaragua, after influenza circulation exceeded the elevated threshold, it has declined over the past four EW to levels below the epidemic threshold, and SARS-CoV-2 circulation remains low. However, RSV positivity rates have risen to levels similar to the peaks observed in previous seasons. • In Panama, ILI and SARI cases, following the increase observed in previous weeks, have experienced a slight decline over the past four EW. Most positive cases are attributable to RSV, whose activity has shown a significant increase, and to a lesser extent, SARS-CoV-2, whose activity remains low. Additionally, influenza activity has remained below the epidemic threshold. Andean ILI and SARI activity has shown a decline over the past four EW in most countries. Additionally, there has been an increase in the proportion of positive SARS-CoV-2 cases, with a decrease in the proportion of positive RSV and influenza cases, whose activity has continued to decline during this period. The predominant influenza viruses have been A(H3N2). RSV activity has remained stable at moderate levels, while SARS-CoV-2 activity has remained at moderate levels compared to previous waves. By country • In Bolivia, SARI cases are fluctuating around the epidemic threshold. Influenza activity has decreased to levels below this threshold. SARS-CoV-2 and RSV activity remain low. • In Colombia, SARI activity, after reaching epidemic levels in recent weeks, has declined below this threshold. Most positive cases are attributed to RSV, whose activity is declining, and to a lesser extent, SARS-CoV-2, which shows circulation levels similar to the peaks observed in previous waves. Acute Respiratory Infection (ARI) cases have decreased to epidemic levels. • In Ecuador, SARI and pneumonia activity has remained at epidemic levels over the past four EW. Positive SARI cases are mainly attributed to influenza, which is at epidemic levels, and to a lesser extent, RSV and SARS-CoV-2, which is on the rise. • In Peru, an increase in SARS-CoV-2 activity has been observed, although at levels lower than in previous waves. RSV has shown a decrease, and influenza activity remains below the epidemic threshold. • In Venezuela, there has been an increase in influenza activity, rising above the epidemic threshold, and a slight increase in RSV activity, which remains at low levels. Brazil and the Southern Cone Following the increase observed in previous weeks, SARI activity has shown a decline over the past four EW, with most positive cases attributable to RSV. ILI activity has shown a slight uptick, associated with an increase in the proportion of positive SARS-CoV-2 cases. Influenza activity is declining, remaining below the epidemic threshold in most countries. During this period, the predominant influenza viruses have been A(H1N1)pdm09 and A(H3N2). RSV activity has shown a slight decrease after reaching levels below the peaks observed in previous seasons. SARS-CoV-2 activity has remained low, although showing a slight increase. By country • In Argentina, ILI activity, after reaching high levels, has declined to levels below the epidemic threshold, while SARI activity, after reaching epidemic levels, has also fallen below this threshold. Influenza activity, after reaching high levels, has declined to epidemic levels. Meanwhile, RSV, after reaching positivity levels similar to the peaks observed in previous seasons, has shown a declining trend, and SARS-CoV-2, although at low levels, has shown a slight increase. • In Brazil, ILI and SARI activity has declined to levels below the epidemic threshold. Influenza activity is also decreasing below the epidemic threshold, while RSV activity remains low. However, SARS-CoV-2 activity has shown a slight increase, though it remains low. • In Chile, after the decline observed in previous weeks, there has been a rebound in ILI and SARI cases, with extraordinary and moderate levels, respectively. Most positive cases during the past four EW are attributable to RSV, whose activity remains elevated, although with positivity levels below the peaks observed in previous seasons. Influenza activity, after reaching extraordinary levels, has declined below the epidemic threshold. • In Paraguay, SARI activity remains at moderate levels, with most positive cases attributable to RSV, whose activity is declining, and to a lesser extent SARS-CoV-2, which is increasing. ILI activity, after reaching epidemic levels, has declined below this threshold, though showing a slight increase in the last week. • In Uruguay, SARI activity has shown a slight decline to epidemic levels, withmost positive cases attributable to RSV, whose activity has reached positivity levels higher than the peaks observed in previous seasons.